1. Field of the Invention
The invention relates to the field of image reproduction with photosensitive elements, particularly those comprising polymeric layers, which are peeled apart in the process of forming images. Such elements are particularly useful for image reproduction and for color proofing and related photomechanical uses, e.g., as lithographic transparencies, photomasks, photoresists, etc.
2. Description of the Prior Art
The prior art describes a variety of photopolymer elements and processes of use, which include producing an image by toning unexposed areas of a photopolymer layer, by image transfer, and producing an image by peeling a photosensitive element apart. In addition, such prior art as U.S. Pat. Nos. 3,469,982 and 3,526,504 describe producing a resist image from an imagewise exposed photopolymerizable or photocrosslinkable layer by washing out the unexposed areas of the layer. The elements of the prior art each have a specific utility and likewise have limitations which limit their usefulness in other applications. For example, in the development of photoresists, incomplete washing out of the unexposed areas of the photoresist layer may result in defective printed circuits due to incomplete plating or etching. An element is needed for photoresists, graphic arts and other applications which can produce a polymeric image in the positive-working mode by complete solvent development and which can produce images of colored polymeric material having a high optical density without interfering with the characteristics of the photosensitive element. The elements of the prior art are also limited in the materials that can be used to provide a proper adhesion relationship, and peel apart elements of the prior art may have pinholes in the image due to improper adhesion. Adhesive values of prior art peel apart elements are typically below 20 g/inch with differences between exposed and unexposed areas being a fraction of this value. Such peel apart elements are characterized in the publication "Image Formation by Photoadhesion" by Woodruff et al., Photographic Science and Engineering, Vol. 11, No. 2, pp. 93-97, March-April 1967. Because of their limited image fidelity such peel part systems are restricted to less demanding uses, e.g., engineering drawings, etc.